A seatbelt for a passenger vehicle typically has a seatbelt retractor that serves to retract the belt into its housing. The belt is wound upon a spool in the housing. When the belt is drawn or protracted from its housing, the spool winds a retraction spring, which later retracts the unused portion of the belt onto the spool or withdraws the belt into its housing when not in use.
In the event of a crash, the seatbelt retractor has a lock that prevents the seatbelt from extending further from its housing. The lock may be actuated by an inertial sensor, which responds to changes in vehicle speed during the crash. When a large deceleration is detected, the inertial sensor triggers the lock of the seatbelt retractor to lock the spool and thereby secures the safety belt in place during the crash.
The inertial sensor has an inertial sensor mass that moves in response to changes in speed of the vehicle. This mass is mechanically linked to the lock by an actuator. When the mass moves, the actuator moves and causes movement of a locking pawl that locks the lock when the mass has moved in excess of a predetermined amount. The actuator rests on a surface of the mass. This surface is typically angled so that movement of the mass causes rapid movement of the actuator and consequently the locking pawl. While rapid movement of the components of the inertial sensor and lock are desirable for safety, this same feature causes undesirable noise during normal vehicle operation. Another source of retractor rattle involves intermittent contact between the sensor actuator and the sensor mass as the actuator bounces on the guide surface of the sensor mass, a rattle noise can be heard. Typically, this noise can be reduced by cushioning the guide surface with a soft material. This, however, can reduce the sensitivity of the sensor mass by creating undesirable friction between the contacting surfaces of the actuator and the guide surface. As an alternative noise absorbing wraps around the retractor assembly have been added which reduce audible noise levels in the passenger compartment of the vehicle. These solutions increase cost and in some cases reduce the inertial sensor's responsiveness.
A need therefore exists for a seatbelt retractor that reduces noise from the foregoing moveable parts.